Connect with us

RCA TV - Model: F32665 / Chasis:CTC203CX

Discussion in 'Electronic Repair' started by Guy Petty, May 1, 2004.

Scroll to continue with content
  1. Guy Petty

    Guy Petty Guest

    Hello all,

    I have an the following TV

    RCA - Model #F32665
    Chasis #CTC203CX

    A friend of mine owned this unit for a few years, and it reciently
    went out on him. His story is that one morning he went to turn on the
    TV, and when he turned on the power to the room the TV made a loud
    buzzing sound. He asked me to look at it (I'm a Computer Tech, have no
    idea what he was thinking) - but anyways, I dont know enough about
    TV's to start tearing stuff up.

    Well - he just went and baught a new one instead of looking at the
    repair option and asked me if I wanted it.

    I took the TV apart, trying to track down the source of the sound.

    pictures are here

    http://www.gpetty.com/TV/

    I cant specifically tell where the sound is coming from, just hard to
    tell, but the pictures are of the general area.

    I probably wont get it repaired either, the nearest place is about 45
    minutes, and with the quote they gave me to just come out, I could buy
    a new 32" TV.

    If I cant fix it......what is the proper disposal of a TV of this
    sort?

    Thanks for any advice.
     
  2. David

    David Guest

    Where do you live?
    Do a Google groups search for that chassis for lots of information and tips.
    Aslo read www.repairfaq.org for some other hints, especially the safety
    section.

    If you do not want to take it on, and are close to N.E Indiana, I will take
    it. (as long as it was not dropped or set outside in the rain)

    David
     
  3. Ken Weitzel

    Ken Weitzel Guest

    Described as buzzing - perhaps the vertical output
    transformer (or whatever the younger fellows call it
    nowadays :)

    Or, how about the degaussing coil?

    Just thinking out loud...

    Ken
     
  4. Jason D.

    Jason D. Guest

    32" is worth fixing! It is not that old YET, CTC203 was only around
    since late 1999.

    Errr.... The deguassing circuit cycles once at each turn on for that
    chassis.

    Contstant "buzzzzzzzz!" is the power supply noise becasue of short
    circuit. Not healthy and will blow out three more transistors & a
    small resistor. Maybe a fuse depending how power supply main
    transistor blows. If left plugged in too long.

    Plug that 32" tv again, chances the power supply will blow. This
    buzzing noise is the power supply trying to power into a short
    circuit. That short circuit is caused by shorted horizontal
    transistor for the flyback transformer. Reason for this short can be
    either the L14401 coil (small round bar wrapped around with length of
    copper magnet wire has hot melt glue on it. Glue broke the solder
    connection on one pin. Look at L14401 solder joint real carefully.
    It is very tiny break. Resoldering is short term fix. Unsolder and
    remove coil, remove glue, Unplug any glue clogged that hole that wire
    went through for that bad solder joint. Reinstall coil and resolder.
    Replace horizontal transistor, RCA part number 237470. Test fit that
    replacement transistor with one middle pin formed to fit through three
    holes WITH transistor flat to the heatsink with all three leads loose
    in their holes. Get small bit of heatsink grease on back of
    transistor and clamp it in place like you do with a CPU and heatsink.
    In thin layer please. Trim excess length and solder. Reassemble set
    with all wires in their original positions in their holders.


    Secondly, this might be a bad flyback transformer. Look carefully for
    a tiny pinhole. This usually happens mostly on 32" and 36" ctc203
    models uses same fly and same fly for either two. Not often but does
    happen. Cost of that fly is only about 60.

    Anyway, get the set in for estimate at good RCA shop (preferably
    authorized if you're not comfortable getting into it.

    Btw, this glue thing is fairly common.

    Cheers,

    Wizard
     
  5. Art

    Art Guest

    Haven't seen a "Vertical Output Transformer" in a few decades of TV design.
    Squeal from the SMPS is indicative of excessive loading, quite often caused
    by a shorted Horizontal Output Device. This can be caused by failure of the
    LOPT, failure of caps in the deflection circuit (rare), and poor, glue
    coated connections of L14401, which has already been addressed. Have a local
    shop have a go at the tele, giving you an estimate before repairing it.
    LOPT, H Output, Repair of L14401 area normally will get these sets up and
    running. Nominal cost should run btw $125 - $200 pending on shop charges,
    etc. IMHO you can't purchase a quality 32" tele for that charge.
     
  6. Guy

    Guy Guest

    Thanks for all the info - it's more of a project now, a few of my
    friends and I are tinkering with it a bit, following all the safety
    precautions.

    It's hard to narrow down the sound, and I'm not familiar with all the
    "exact" terms for each item on the circuit boards.

    The noise is similar to an alarm clock buzzing, although not as loud.
    We plugged it in a few minutes and it just remained buzzing. (I know,
    not the best thing, but the original owner left it on a few hours
    running like that, figured it couldn't get much worse).

    http://www.gpetty.com/TV2/

    I put an edited picture on there, to give a general idea of where the
    sound is coming from. And other small notes.

    We are going to be bringing home testing equipment from the labs at
    work to fool around a bit more, but before we started tearing it apart
    to test and such, I figured we'd ask.

    I'm going to be reading the webpages on this chasis, and I appreciate
    the input.

    Guy
     
  7. Jason D.

    Jason D. Guest

    Hi Guy,

    To localize noise techs uses either steroscope or a listen through a
    Mcdonald's drinking straw at item in turn. Extremely effective. (I
    keep few of them in toolbox and invite one of my tech or boss to help
    me find it. I'm deaf and can't hear small noises.

    But on CTC203, I rather not blow it up more, order the RCA part number
    237470 first. Check the Q14401, it WILL be shorted. Hence the buzz
    noise. transistor is marked clearly on the circuit board and this
    horizontal output transistor is clamped down with wide spring steel
    clamp. If you have a plastic goes from square metal box running
    across horizontal transistor to the power supply's heatsink. Take it
    out and toss it. This plastic strap chokes the air flow for that
    horizontal heatsink which is Bad Thing but good thing yours did not
    have it.

    Reason you hear buzz or squeal is the all SMPSes either or both
    increases the "on" time and or decreases frequency to pump "Scotty,
    more power!" This reasoanaces changes and made audible from parts
    vibrating. More power to loads if power demands incrases to keep
    voltage as stable as possible, some SMPS simply blows that instant
    like in Sony. Shorted horizontal transistor is easily found with a
    ohm meter (DMM).

    Heating up is also consistant with bad parts that is shorted but this
    is very misleading because the good parts does heat up more trying to
    pump more power to something else. Also this is how some cases lets
    out magic "smoke" that stink that goes with it.

    Heating up pointing to the small board is the pincushion circuit to
    correct pincushioning error on some CRTs. Not all models has this
    active pincushion. Very nice set indeed.

    Below that pincushion board, right at the mainboard you will see a
    small coil which is L14401 right next to base of heatsink of
    horizontal transistor where that small board is mounted to that said
    heatsink. On other side of that heatsink is the Q14401 horizontal
    transistor with wide steel spring clamp which you will find shorted.

    Fix the L14401's glue and replace Q14401 (part number 237470) will get
    that tv fixed.

    That Q14401 grounds B+ through flyback tranform to put energy into the
    magnetic field of the ferrite core in linear fashion and horizontal
    yoke winding. B+ is 140V typically measured from cold side ground, the
    SMPS transformer is the isolation but it is still hot chassis since
    the SMPS circut is still hot direct to line power). Grounding B+ via
    flyback transformer during beam motion just before vertical centre of
    crt's face and that transistor turns off at end of scan and capacitors
    and diodes, windings in both coils and flyback oscillate from back EMF
    in orderly way to kick beam from left to right and fall back to the
    centre at correct speed, process repeats.

    This horizontal circuit exacts very heavy demand on that transistor
    and have to be designed carefully during design stage of a TV.
    Normally could radiate about 40W during worst cases during horizontal
    transistor's turn on and turn off part of pulses, hence the heatsink
    for it. Anything wrong in that horizontal circuit that transistor
    goes instantly with a snap of fingers. Just one bad pulse or bad part
    anywhere in the horizontal circuit is enough. One of those killer
    parts like glue that cracked L14401's solder joint will do that. That
    L14401 coil is the part between horizontal transformer driver (T14301)
    and the horizontal transistor's base pin.

    Injecting small amount of current into base pin on BJT transistors
    controls amount of current going C (collector) to E (emitter) in turn
    vary the voltages, this is how audio amp does or as a voltage
    regulator, etc. Also can be controlled fully on for full on or fully
    held low for off such as for computer, horizontal transistor for
    horizontal circuit applications.

    Reason TVs needs horizontal transformer driver is impendance matching
    and to turn low current into high current drive with very tiny volts
    and ablity to pull base negative for tiny time as required to force
    horiozntal transistor off while in satrated mode. Malformed waveforms
    on base drive or bad parts anywhere in horizontal circuit upsets the
    tuning in turn changes waveforms, this blows that transistor because
    transistor isn't turned on or off properly or way too slow or too
    fast.

    Also that is reason this particular transistor is required for
    reliable operation, poor horizontal transistor substutition won't work
    and also there is so many fake transistors out there, hence reason for
    ordering that one from RCA.

    I've been burned by fake parts in past. Wastes time and makes
    customers unhappy with repeats (aka call backs). Choosing good
    supplier is important for us and knowing which supplier does and what
    doesn't is good to know.

    Cheers,

    Wizard
     
  8. Art

    Art Guest

    Right On, Jason: Have a person that endures bi-lateral Tinnitus with
    accompanying Hypertussis try to diagnose a ringing deflection circuit. Any
    listening devices that can be safely applied are an asset. I personally use
    a piece of plastic rod.
     
  9. Guy

    Guy Guest

    Wow, followed the directions and we got it working!

    Was right on with the problem!

    My hats off to the TV techs out there..

    Guy
     
  10. Art

    Art Guest

    Thanks Guy, many times info is presented but not followed. The whole group
    acknowledges your pleasent response.
     
  11. Jason D.

    Jason D. Guest

    Bravo!!! Guy! Adjust the focus, by the way, on those RCA from factory
    is bit off-focus. Very nice set and will last long time if you get
    that glue out of that tiny teensy hole.

    And Art's is in agreement with mine.

    Cheers,

    Wizard
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-